This Project will examine the link between selected glial neuroinflammatory responses and neuronal cell death. The hypothesis to be tested is: Overproduction or sustained production of potentially detrimental biomolecules (NO and pro-inflammatory cytokines) by activated glia contribute to neuronal death. Insight into which of these pathways can be readily modulated by endogenous factors or synthetic ligands will provide a firm foundation for future drug discovery efforts towards developing new therapeutics for Alzheimer's Disease (AD). We will address several fundamental questions about glial cytokine production and its linkage to neuronal cell death. These include: what glial cytokines contribute to neuronal death and what pathways are potential targets for inhibition of cytokine-dependent neuronal cell death? The focus will be on: (i) beta-amyloid (Abeta)-induced upregulation of inducible nitric oxide synthase (iNOS), and its potentially neurotoxic product, nitric oxide (NO) and NO metabolites such as peroxynitrite; (ii) the Abeta-induced increases in proinflammatory cytokines interleukin (IL)-1beta, tumor necrosis factor (TNF)alpha, and S 100B; (iii) comparison of the neurotoxic effects of these glial derived products to those of direct Abeta effects on neurons; and (iv) discovery of ligand modulators of signaling pathways key to neuronal cell death. In aim 1, we will define at the molecular level what is meant by glial cytokine-dependent neuronal cell death. Glial/neuronal co-culture models, in vivo administration of cytokines, and animal models of neuroinflammation and disease will be utilized. We will determine the potential common and distinct elements between cytokine-dependent and -independent neuronal death by focusing on key elements of standard themes that have been implicated previously in cell death mechanisms, particularly MAP kinase (MAPK)-regulated pathways and death domain signaling pathways involving death receptors like TNF receptorl (TNFR1) and death kinases like death associated protein kinase (DAPK). In aim 2, we will discover ligand modulators of cytokine-dependent neuronal cell death. Chemical genomics approaches will allow the discovery of small molecule modulators of neuronal cell death and death kinases. Pathway selective inhibitors will allow probing of the relative contribution of distinct signaling pathways to common biological end points. Potentially efficacious synthetic compounds will be tested in animal models of neuroinflammation and disease. Our results will have a potential broad impact on basic restarch in areas such as signal transduction and glialneuronal interactions as well as provide insight into possible new therapeutic approaches to neurodegenerative disorders such as Alzheimer's disease.